High-speed cell search system for CDMA

ABSTRACT

In a high-speed search system for CDMA, plural (M) symbols which are subjected to spread frequency coding with a spreading code called as a short code are prepared when synchronization of the spreading code is established before synchronization of carrier is established in a mobile station used in a CDMA cellular system, data which are obtained by forming an orthogonal code with the polarities of the M symbols are set as a down signal, and when the orthogonal code concerned is detected, coherent integration is performed by a correlator having combinations of the polarities which can be possibly taken by the code over the plural symbols (of M) constituting the code.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a high-speed cell search system forCDMA, and a high-speed search circuit for use in a CDMA (Code DivisionMultiple Access) communication system having larger interfering wavecomponent power than target signal component power, and moreparticularly to a high-speed cell search system in which S/N(Signal/Noise) is increased by performing coherent integration overplural signals for search, and identification and screening of longcodes are performed by using an orthogonal code.

(2) Description of the Related Art

In a CDMA cellular system, a mobile station must establishsynchronization of a spreading code sequence before it establishessynchronization of carrier and clocks. It may take long time toestablish the code synchronization, and it is a critical problem forCDMA to shorten this time. Specifically, the conventional CDMA cellularsystem has the following two problems.

A first problem is as follows. That is, the mobile station performs acell search for detecting a connection cell on the assumption of anestimation method of initial synchronization of spreading codes.

Conventionally, in an inter-base-station synchronization system which isrepresented by IS-95, the respective base stations synchronously operatein cooperation with one another on the basis of a predetermined offsetamount, and thus each base station 1 can perform the cell search work byusing only one type of spreading code even when it moves from one basestation to another base station, so that the search time can beshortened.

However, in order to use this method, the base stations are required tobe synchronized with one another, and in order to satisfy thisrequirement, a system for generating a reference synchronous signal toestablish external synchronization between the base stations isseparately needed.

Therefore, an inter-base-station asynchronous system which needs noexternal system has been required. However, each base station cannothave one common spreading code because the base stations areasynchronous therebetween. Therefore, the respective base stations havedifferent kinds of spreading codes, and thus all kinds of spreadingcodes must be searched in a process of acquiring and following theinitial synchronization, resulting in increase of the search time.

A second problem is as follows. A method of acquiring synchronizationand following synchronization on the basis of an coding gain by aViterbi processor provides high-quality data on convolution-encodedinformation. However, at the time when the synchronization of thespreading code sequence is established, the Viterbi processor does notoperate because it is before data are read in, and thus the detection isperformed in the state that there is no coding gain. Since nothing isstarted (for example, no carrier synchronization is started) unless thesynchronization establishment is completed, it is necessary to performthe detection with high quality even when there is no coding gain. Thatis, if there is some probability that erroneous detection occurs, therepetition of the search work would occur, resulting increase of thesearch time.

SUMMARY OF THE INVENTION

The present invention relates to a search system for use in CDMA havingbig interference compared with target signal power, and moreparticularly to a cell search of a long-code mask system for performinghigh-speed search by using a long-code mask symbol which is subjected tospread spectrum coding with only a short code.

According to the long-code mask system, in a CDMA inter-base-stationasynchronous cellular system, symbols which are subjected to the spreadspectrum coding with a long code are masked in a fixed period to providesymbols (mask symbols) which are subjected to the spread spectrum codingwith a short code, and a mobile station implements a high-speed cellsearch by using the mask symbols (disclosed in “Technical Reports RCS96-74 of Radio Communication System Research of Electronics InformationCommunication Associates).

According to the long-code mask system which has been open to the publicuntil now, the timing of the long code is detected by utilizing the masksymbol based on the short code, and then the long code is identified byusing a normal sliding correlator. Accordingly, for example, when thenumber of users is increased to magnify interfering wave power, theprobability that the erroneous detection occurs is increased, and therepetition of the search occurs, resulting in increase of the searchtime. Further, when the number of long codes to be identified isincreased, the search time is also increased.

On the other hand, according to the present invention, identification orscreening of a long code is enabled by L-time repetition of M masksymbols of the long code (L<M). Further, coherent integration isperformed over M symbols to enhance SNR (Signal-to-Noise Ratio), andspecification or screening of the long code is performed at an earlystage while reducing the error-occurring probability, therebyimplementing the high-speed cell search.

Further, according to the present invention, in a CDMA system whichimplements the inter-base-station asynchronous system by performing thespread spectrum coding every base station on the basis of codes whichare called as “long codes inherent to the base stations”, datacomprising orthogonal codes which are constructed by M symbols are addedwith information for specifying a base station, and the screening orspecification of the long code is performed on the basis of theinformation, so that the high-speed cell search can be implemented.

Further, the present invention is applicable to orthogonal demodulationhaving I-system and Q-system, and the higher-speed cell search can beperformed by performing power addition after the coherent integration isperformed.

Still further, the present invention can be implemented with a smallscale of circuit by a ring buffer for performing an adding operationwith the polarity corresponding to an orthogonal code, so that thepresent invention is suitably applicable for power save.

According to the present invention, a Barker sequence is used to specifythe frame position, and thus data constructed by orthogonal codes can beprevented from being erroneously detected as a frame synchronizationsignal.

The present invention is applied to a serial search, a parallel searchor a serial/parallel mixed search, and a parallel degree, that is, asearch detection time can be selected in accordance with an achievablecircuit scale, thereby making the design flexible.

According to the present invention, by providing redundancy to datawhich are constructed by the L-time repetition of the orthogonal codesbased on M symbols, data for specifying a long code which is defecteddue to fading or the like can be restored, thereby reducing the retryfrequency of search and shorten the search time as a whole.

Further, according to the present invention, the synchronization of thespreading code sequence is required to be established before the carrierand clock synchronization is established, however, the high-speed searchcan be performed by performing the coherent integration corresponding tothe frequency deviation with a relatively small-scale circuit even inthe state that there is a carrier frequency deviation.

A search system for CDMA according to the present invention ischaracterized in that plural (M) symbols which are subjected to spreadfrequency coding with a spreading code called as a short code areprepared when synchronization of the spreading code is establishedbefore synchronization of carrier is established in a mobile station,data which are obtained by forming an orthogonal code with thepolarities of the M symbols are set as a down signal, and when theorthogonal code concerned is detected, coherent integration is performedby a correlator having combinations of the polarities which can bepossibly taken by the code over the plural symbols (of M) constitutingthe code.

Further, in a CDMA system which implements an inter-base-stationasynchronous system on the basis of a code called as a long codeinherent to a base station, data constructed by the orthogonal codecontain information to specify a base station, and specification orscreening of a long code is performed on the basis of the information.

Still further, in the present invention, one code of the orthogonalcodes is used as a header.

In the present invention, the symbol data of M which are received on thebasis of the combination of the polarities determined by the orthogonalcodes are added in the in-phase component and the quadrature component,an orthogonal vector which is received on the basis of the square sumthereof or the maximum value of the amplitude component is specified,and the screening or identification of the long code is performed on thebasis of the data obtained by the L-time repetition of the aboveprocessing.

Further, in the present invention, an M-tap ring buffer which performsaddition with the polarities corresponding to the orthogonal codes ineach of the I-system and the Q-system is provided, the content of thering buffer is renewed at a symbol rate and the addition result is usedto specify an orthogonal vector.

Still further, in the present invention, a Barker sequence is used tospecify the frame position of the M symbols.

In the present invention, the above function is applied to serialsearch, parallel search or serial/parallel mixed search.

In the present invention, redundancy is provided to codes which areformed by L-time repetition of an orthogonal vector to provide afunction of restoring a portion which cannot be detected.

Further, in the present invention, in the coherent integration operationof the M symbols, a sequence which is weighted and polarized on theassumption of the carrier frequency deviation is prepared, and themaximum one is selected on the basis of the correlation thereof, therebysupporting coherent integration having frequency deviation.

Still further, in the present invention, in the coherent integrationoperation of the M symbols, when a sequence which is weighted andpolarized on the assumption of the carrier frequency deviation isprepared, the approximation is performed by using only the polarities.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a first embodiment using a high-speed cellsearch system in a CDMA communication system of the present invention;

FIG. 2 is a table showing the relationship between symbol addition andorthogonal code;

FIG. 3 is a diagram showing a signal status based on time integrationand coherent integration per unit signal;

FIG. 4 is a diagram showing the frame construction;

FIG. 5 is a timing chart when long-code identification is performed byL-time repetition of an orthogonal code of M symbols;

FIG. 6 is a diagram showing a second embodiment of a cell search circuitwhen the present invention is applied to orthogonal detection;

FIG. 7 is a block diagram showing the overall cell search containing along-code identification circuit;

FIG. 8 is a diagram showing a search circuit with an coherentintegration function using RAM;

FIG. 9 is a diagram showing a symbol addition polarity correctionrotational feather of carrier frequency deviation supporting coherentintegration; and

FIG. 10 is a symbol addition polarity correction table of the carrierfrequency deviation supporting coherent integration.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A preferred embodiment according to the present invention will bedescribed hereunder with reference to the accompanying drawings.

FIG. 1 is a diagram showing a first embodiment using a high-speed cellsearch system in a CDMA communication system according to the presentinvention.

In FIG. 1, a spread spectrum signal is input to a base band signaldecoder 7 to decode the spread spectrum signal to a base band signal,and then the base band signal is input to an A/D converter 6 to beconverted to a digital signal. The reception signal after the A/Dconversion is multiplied by the output an(k) of a spread spectrum signalgenerating circuit 1-1 with a phase shift function to perform andespread spectrum coding. The multiplication result is stored in anaccumulator which comprises an adder 4-1 and a one-signal buffer of aring buffer 3-1, thereby implementing a function of performing timeintegration in an unit signal cascade time period before the spreadspectrum coding. The signal before the spread spectrum coding is notvaried during an unit signal section, and thus the despread timeintegration result becomes a signal before the spread spectrum coding.

A first part of FIG. 3 represents a timing chart representing the abovestate. In FIG. 3, the time integration per unit time is accumulated withtime lapse, and a noise component is also integrated. However, theincrease of the noise component is smaller than that of the signalcomponent, and this enhances the SNR.

Returning to FIG. 1, the operation of performing the time integrationover unit signal as described above is also performed on a next signalin the same manner. However, at this time, the ring buffer is rotatedand the integration result is accumulated in a new buffer. The operationis also performed on M of the ring buffer. When the final integrationoperation is completed, the symbol addition on the content of eachbuffer is performed according to the polarities shown in FIG. 2. FIG. 2shows an example of the relationship between the polarity of the symboladdition and the orthogonal code, and it shows a case for M=4. When thesame operation is applied to each orthogonal code shown in FIG. 2, theaddition result is maximum at the time when the patter of M signalsbefore spread spectrum coding is coincident with the combination patternof the polarities. FIG. 3 shows the time integration state under thecoincidence between these patterns. In FIG. 3, those portions which arerepresented by black dots and arrows represent the integration resultaccumulated in the buffer. FIG. 3 shows the aspect that SNR is enhancedby performing the addition operation at M times. Here, FIG. 3 shows thesignal status based on the time integration and the coherent integrationper unit signal. As shown in FIG. 2, corresponding data are allocated toeach orthogonal code, and the corresponding data can be identified bydetecting the maximum value. By this operation, that is, the coherentintegration, in the data accumulated in each buffer, the power of theaddition result is represented by the following equation due tostatistical independence:E[{X ₁ +X ₂ + . . . +X _(M)}² ]=E[X ₁ ² +X ₂ ² + . . . +X _(M) ² ]=M*E[X²]  (1)Here, the random variables X₁, X₂, . . . , X_(M) has the probabilitydistribution, and they are represented by X.

Since the power of the addition result of the signal S is M²S², if it isconverted to the level, it is found out that the signal component isincreased by M times and the noise component is increased by M^(1/2)times through the addition operation at M times, so that the SN ratio isenhanced by M^(1/2) times.

In the case of the CDMA communication system, the noise component islarger than the signal component, and an expected SN ration cannot beobtained by merely performing the time integration at the same level asthe unit signal duration before the spread spectrum coding. However, bythe above method, the SN ration can be increased by M^(1/2) times, andthus the judgment for the synchronism acquisition of the spread spectrumsignal can be implemented.

Next, the operation of acquiring the synchronization of the spreadingcode on the basis of the judgement result will be described.

In FIG. 1, the serial search and the parallel search are mixed with eachother with the parallel number set to k in order to shorten the searchtime. In FIG. 1, a parallel-arranged k-th block is illustrated, and kblocks having the same construction are arranged to form one searchcircuit. Each of spread spectrum signal generating circuits with phaseshift function 101 to 1-k has a fixed phase shift, and the additionstart position for the unit signal of each of the ring buffers 3-1 to3-k is also shifted due to the above phase shift. Accordingly, thesynchronization acquisition of the spreading code can be performed onthe basis of the maximum value of the correlation value corresponding toeach correlator.

FIG. 6 is a diagram showing the overall construction when the CDMA cellsearch circuit of the present invention is applied to orthogonaldetection. In FIG. 6, 10-1, 10-2 represents the same cell search circuitas used in the first embodiment of FIG. 1. Selectors 11-1 and 11-2 areused to select an addition output of the ring buffer, and it is set tobe selected when each ring buffer is in full state. At this time, if anamount of phase shift in unit signal length+phase shift of unit symbollength is given to the timing of each ring buffer addition and thespreading code for the ring buffers of k, it is available to dispersethe load of the processing of the sectors and subsequent stages.Multipliers 12-1 and 12-2 and an adder 15 are used to take the squaresum of each of I and Q and detect the power. A shift register 13 and aspread spectrum signal generating circuit with phase shift function 14are used to supply the multipliers in the cell search circuits 10-1 and10-2 with the spreading code for despread coding. In this embodiment,each of the in-phase component and the quadrature component uses BPSK(Binary Phase Shift Keying) spread spectrum coding using the samespreading code, and thus the spreading codes a1 to ak from the shiftregister are commonly used. Further, a1 to ak are obtained byphase-shifting the same code, and thus they are supplied from the shiftregister while varying the phase thereof.

The signal which is converted to power by the square addition of I, Qafter the synchronization addition of M is performed as described above,is subjected to power addition over L frames by an L-frame power adder16, thereby suppressing the effect of Rayleigh's fading.

At this time, it is needless to say that an absolute value circuit isused in place of the power conversion in the power detection to suitablyreduce the circuit scale.

The orthogonal code is received as described above, and the frameconstruction thereof is shown in FIG. 4.

The present invention relates to the high-speed cell search in theinter-base-station asynchronous system, and base stations use differenttypes of spreading codes. Therefore, all the types of spreading codesare searched in the initial synchronization process. If this operationis directly carried out, the search time is necessarily induced.Therefore, the high-speed search is performed by using long-code masksymbols which are subjected to the spread spectrum coding with onlyshort codes. The hatched portion of the frame construction of FIG. 4represent long-code mask symbols.

In this embodiment, an orthogonal code constructed by M symbols isperiodically transmitted, and information to screen (or specify) onelong code is represented by L frames. One of the L frames is used as aheader of the information, and long codes of (M−1)^(L−1) can beidentified. Further, the orthogonal code uses a part of the frame, and acorrelation appears at a symbol interval in the long code mask symbols.Therefore, the specifying precision of the position in the frame of theM symbols can be enhanced by using a Barker sequence having a sharpauto-correlation. FIG. 4 shows the frame construction at this time. Whenthe L frames of the M orthogonal codes are detected, the timing of theshort code, the timing of the long code and the identification of thelong code are achieved, and thus the correlation detection of the longcode can be performed on the basis of the above factors. Therefore, thelong code candidates can be screened at an early stage by transmissionof long code candidate information in the long code mask symbol.

Here, since the cell search just after power is turned on is underinitial synchronization, the detection is required to be performed inthe state that phase shift of carrier is appended. Accordingly, thepolarity of the received symbol is unknown. However, according to thepresent invention, an orthogonal vector such as Hadamard's matrix, Walshmatrix or the like of the M symbols is assigned as the M symbols, andthus the detection can be performed even with being accompanied by thephase deviation of carrier. The position of the M symbols of L may beassigned every frame as in the case of FIG. 4, or they may becollectively arranged within one frame.

FIG. 5 shows the aspect of the identification of the long code asdescribed above. In FIG. 5, a first section of ν symbols represents asection in which the short-code synchronization is established, and thefirst orthogonal code is detected in this section. Subsequently, theresidual orthogonal codes of L−1 is detected in a section of L symbols.On the basis of the information, the identification of the long code isfinally performed.

The following equation (2) represents the time to examine all the statesof one frame period when the serial/parallel mixed cell search isperformed from FIGS. 1 and 5:ν=(P*S/C)*10 [ms]Here, P represents the short-code period, C represents the number ofparallel processing of the correlator, S represents the number ofsamples per chip, and one frame length is set to 10 ms.

Accordingly, the number C of the parallel processing can be flexiblyselected in accordance with the restriction due to the circuit scale andthe demanded search time. Further, the redundancy may be provided to thelong code information based on the orthogonal codes of the M symbols torestore those portions which cannot be detected due to fading during thedetection of L, thereby enhancing the resistance to fading.

As an example, for ν=8 (80 ms) and L=10, the search time is equal to(8+10)*(10 ms)=180 ms.

FIG. 7 is a block diagram showing the overall cell search containingidentification of the long code. In FIG. 7, long-code timing detectionand long-code candidate detection 20 detects the type of the orthogonalcode and the position thereof, that is, the timing of the long code onthe basis of the combination of the polarities of the above orthogonalcodes. A correlator 21 has a short code generating circuit therein, andoutputs a correlation value obtained by a correlator 29 to an in-phaseadding ring buffer based on a RAM. The ring buffer based on the RAMimplements the same function as shown in FIG. 1 while reducing thehardware scale, and the coherent integration of the combination of thepossible polarities of the orthogonal codes is performed by anorthogonal code control circuit provided in a maximum value detectioncircuit 22.

The coherent integration value of the I-system, the Q-system thusobtained is converted to power in a square sum circuit 24, and theresult is output to the maximum value detection circuit 22. The maximumvalue detection circuit 22 has a chip counter and a symbol counter, andregisters the chip position and the symbol position having the maximumvalue, and the polarity of the orthogonal code at that time into amaximum register. Further, the finally-remaining value is output to longcode identification 25.

The long-code identification 25 performs the data conversion from theorthogonal code on the basis of the information transmitted from thelong-code timing detection and long-code candidate detection 20 todetect the long-code screening information. It identifies the long codeinherent to the base station on the basis of the screened information,The screened information is transmitted to a sequential long-codegenerating circuit 26, and detects the correlation value by a long-codecorrelator 28. On the basis of the detection result, a maximum judgmentcircuit 27 judges the maximum correlative code as the long code.

FIG. 8 shows the details of the in-phase adding ring buffer based on theRAM. Information which is subjected to despread coding by a matchedfilter or a serial/parallel mixed correlator 31 is output to thein-phase adding ring buffer 33 based on the RAM. The in-phased addingring buffer 33 based on the RAM can freely set the polarity to be addedunder the control from the external, and the coherent integration valuecorresponding to the polarity is output to each of the I-system and theQ-system. The maximum value of the square sum thereof is detected by themaximum value detection circuit 32.

FIG. 9 shows the coherent integration when there is a frequencydeviation in carrier between a mobile station and a base station, andthe correction is applied by the rotational feathers corresponding to anadvance frequency (f+δf), a synchronization frequency (f) and a delayfrequency (f−δf) at the symbol addition time. The correlative comparisontarget can be accurately provided with ROM tables of sine and cosine.However, FIG. 9 shows a case that a correlative comparison target forwhich the frequency deviation is corrected by a simple circuit with noROM table is provided, and the phase rotation due to the frequencydeviation between symbols is set to π/2 with the advance frequency and−π/2 with the delay frequency, and they are implemented by the additionand the subtraction respectively.

FIG. 10 shows a case where the polarities based on the orthogonal codefor m=4 are set to ++++. As show in FIG. 10, this is implemented by thecorrelative comparison addition and subtraction of the coherentintegration at the carrier frequency deviation time.

As described above, according to the high-speed cell search system forCDMA of the present invention, the identification or screening of thelong code can be performed by the L-time repetition of the long-codemask symbols of M, and at the same time the coherent integration isperformed over the M symbols. Therefore, the long code candidates can bescreened at an early stage to shorten the initial synchronization time,thereby providing an excellent CDMA system.

Further, the present invention is greatly effective to shorten thesearch time even under such severe environments inherent to the mobilecommunication that Rake synthesization is not usable for the initialsynchronization just after a source power is turned on, the transmissionpower is dispersed due to multipath, resulting in reduction of thesignal component after the despread coding, the detection must beperformed with being accompanied with the carrier phase shift, etc.

According to the present invention, each of the I-system and theQ-system is subjected to the coherent integration to enhance SNR, andthen the square sum of I, Q is taken to judge the orthogonal code on thebasis of the value of the square sum. Therefore, the present inventionis applicable to orthogonal decoding.

According to the present invention, the content is renewed every symbolrate by the M-tap ring buffer which can perform the coherent integrationwith the polarity of the orthogonal code, and the orthogonal code isidentified on the basis of the addition result. Therefore, there can beprovided a search circuit which is suitable to reduce the hardware andsave power consumption.

Further, according to the present invention, a code having sharpauto-correlation such as a Barker sequence or the like is used tospecify the position of the frame of the M symbols. Therefore, noerroneous recognition is made on a correlation which appears everysymbol, and thus the search time can be shortened.

The present invention is applicable to the serial search, the parallelsearch and the serial/parallel mixed search, and the parallel degree,that is, the search time can be selected in accordance with the circuitscale which can be implemented. Therefore, the design can be madeflexible.

According to the present invention, the redundancy can be provided tothe data constructed by the L-time repetition of the orthogonal codebased on the M symbols, thereby restoring the data for specifying thelong code which is defected due to fading or the like. Therefore, theretry times of search can be reduced, and the search time can beshortened as a whole.

Further, the present invention needs to establish the synchronization ofthe spreading code sequence before the initial synchronization in themobile station, that is, the carrier and clock synchronization isestablished. However, even when there is a carrier frequency deviation,the high-speed search can be performed by the coherent integrationcorresponding to the frequency deviation with a relatively small scalecircuit.

Although the present invention has been shown and described with respectto best mode embodiments thereof, it should be understood by thoseskilled in the art that the foregoing and various other changes,omission, and additions in the form and detail thereof may be madetherein without departing from the spirit and scope of the presentinvention.

1. A high speed searching circuit for use in a CDMA cellular systemhaving a plurality of mobile stations and a plurality of base stations,comprising: a detection circuit which receives a plurality of shortcodes which are orthogonal with each other and a long code inherent toone of said plurality of base stations, and correlates the received datawith said plurality of short codes to detect said one of said pluralityof short codes contained in said received data; and a long code judgmentcircuit which screens candidates for the received long code on the basisof the detected short code.
 2. A mobile station for use in a CDMAcellular system having a plurality of mobile stations and a plurality ofbase stations, comprising: a detection circuit which receives aplurality of short codes which are orthogonal with each other and a longcode inherent to one of said plurality of base stations, and correlatesthe received data with said plurality of short codes to detect said oneof said plurality of short codes contained in said received data; and along code judgment circuit which screens candidates for the receivedlong code on the basis of the detected short code.
 3. A base station foruse in a CDMA cellular system having a plurality of mobile stations anda plurality of base stations, comprising: a short code generator whichgenerates a plurality of short codes which are orthogonal with eachother; and a transmitter which transmits, to said plurality of mobilestations, data containing one of said plurality of short codes and along code inherent to the base station.
 4. A CDMA cellular system,comprising: a plurality of mobile stations; a plurality of basestations, each of the base stations comprisings, a transmitter whichtransmits, to said plurality of mobile stations, data containing one ofa plurality of short codes which are orthogonal with each other and along code inherent to the base station, and each of the mobile stationscomprising, a detection circuit which receives a plurality of shortcodes which are orthogonal with each other and a long code inherent toone of said plurality of base stations, and correlates the received datawith said plurality of short codes to detect said one of said pluralityof short codes contained in said received data; and a long code judgmentcircuit which screens candidates for the received long code on the basisof the detected short code.
 5. The high-speed searching circuitaccording to claim 1, wherein, each of said plurality of short codesincludes a plural (“M”) symbols which are spread spectrum symbols; saidM symbols have combinations of the polarities corresponding to saidshort codes; and said detection circuit have despreading means togenerate M symbols data.
 6. The high-speed searching circuit accordingto claim 5, wherein said detection circuit further comprises: adders foradding said M symbols data in an in-phase component and a quadraturecomponent; and an orthogonal vector which is received on the basis ofthe sum thereof and the maximum value of the amplitude component isspecified.
 7. The high-speed searching circuit according to claim 5,wherein said detection circuit further comprises an M-tap ring bufferfor adding said M symbols data in an in-plane component and a quadraturecomponent in accordance with polarities corresponding to said shortcodes, wherein: the content of said M-tap ring buffer is renewed at asymbol rate, and the addition result is used to specify an orthogonalvector.
 8. The high-speed searching circuit according to claim 5,wherein a Barker sequence is used to specify the frame position of the Msymbols.
 9. The high-speed searching circuit according to claim 1,wherein redundancy is provided to codes which are formed by “L”-timerepetition of an orthogonal vector to provide a function of restoring aportion which cannot be detected.
 10. The high-speed searching circuitaccording to claim 5, wherein, in the coherent integration of the Msymbols, a sequence which is weighted and polarized on the assumption ofthe carrier frequency is prepared, and the maximum one is selected onthe basis of the correlation thereof, thereby supporting coherentintegration having frequency deviation.
 11. The mobile station accordingto claim 2, wherein, each of said plurality of short codes includes aplural (“M”) symbols which are spread spectrum symbols; said M symbolshave combinations of the polarities corresponding to said short codes;and said detection circuit have despreading means to generate M symbolsdata.
 12. The mobile station according to claim 11, wherein saiddetection circuit further comprises: adders for adding said M symbolsdata in an in-phase component and a quadrature component; and anorthogonal vector which is received on the basis of the sum thereof andthe maximum value of the amplitude component is specified.
 13. Themobile station according to claim 11, wherein, said detection circuitfurther comprises an M-tap ring buffer for adding said M symbols data inan in-plane component and a quadrature component in accordance with thepolarities corresponding to said short codes, and the content of saidM-tap ring buffer is renewed at a symbol rate, and the addition resultis used to specify an orthogonal vector.